Data storage in the computer industry is accomplished in a number of ways. For example, data may be stored on tape, compact disk, “floppy” or “hard” disk, and the like. Oftentimes, data storage media which is transferrable from one location to another is housed within a parallelepiped-shaped cartridge. It is to be understood that the term “cartridge” or “data cartridge” as used in the present application encompasses any data storage media device, whether or not it is housed within a cartridge.
Data storage systems are used to store data storage media devices such as data cartridges at known locations and to retrieve desired cartridges so that data may be written to or read from the cartridges. Such data storage and handling systems are often referred to as “juke box” data storage systems, particularly if they can accommodate a large number of individual data cartridges.
A typical data storage system may include different types of cartridge receiving devices. For example, one type of cartridge receiving device is a cartridge storage rack or “magazine” which has a plurality of individual cartridge storage locations that may be arranged in one or more horizontal rows or arrays. Another type of cartridge receiving device is a cartridge read/write device or “drive”.
A data storage system may also include a cartridge access device. Depending on the particular system, the cartridge access device may comprise a cartridge engaging assembly or “picker” which may be adapted to engage the selected data cartridge, withdraw it from its storage location, and carry it to a drive. The drive may then be used to read data from or write data to the cartridge. Once the read/write operation is complete, the cartridge engaging assembly or picker may withdraw the data cartridge from the drive and return it to the appropriate location within the cartridge storage array. In another type of system, the cartridge access device may comprise the drive itself, in which case the data cartridge may be read from or written to without the need to carry the data cartridge to a separate drive.
Regardless of the particular type of cartridge access device that is utilized by the data storage system, the positioning system or translation apparatus used to move the cartridge access device along the cartridge storage array must be capable of moving the cartridge access device along the cartridges stored in the array so that the desired data cartridge may be accessed. One type of positioning system, often referred to as a “lead-screw” system, mounts the cartridge access device on a lead-screw which, when turned, moves the cartridge access device back and forth along the array of cartridges. While such lead-screw positioning systems are being used, they are not without their problems. For example, in such a system the cartridge access device may be cantilevered on the lead-screw which may result in excessive transverse or rotational movement of the cartridge access device. Such excessive movement reduces positional accuracy and may make it difficult for the cartridge access device to reliably engage the desired data cartridge on a repeated basis.
Partly in an effort to solved the foregoing problems, positioning systems have been developed which utilize separate guide rails or tracks to guide the cartridge access device along the array of cartridges. The cartridge access device is mounted to the separate guide rails or tracks and the lead-screw is then used only to move the cartridge access device to the desired location. Alternatively, a wire-rope (i.e., cable) drive system may be used to move the cartridge access device. While such systems generally provide for increased positional accuracy over a simple cantilevered type of lead-screw arrangement, they are still not without their disadvantages. For example, the guide rail or track assemblies usually comprise machined components finished to a high degree of precision, which adds to the overall cost of the data storage system. Moreover, the guide rail or track assemblies are often difficult to align and may become mis-aligned during subsequent shipping or movement of the data storage system. If the mis-alignment is substantial, it may be necessary to re-align and re-calibrate the positioning system before the data storage system can be placed in operation.
A positioning system/translation apparatus for moving a cartridge access device along an array of cartridges has been described in the parent application Ser. No. 09/337,802 (hereinafter referred to as '802). This positioning system provides increased positional accuracy to reduce errors due to mis-alignment of the cartridge access device. As described in '802, this is achieved with a minimum number of components to maximize reliability and reduce cost, yet does not require the use of expensive, precision-machined components and guide rails. The positioning system of '802 also reduces the amount of time required to align and calibrate the assembly during production and reduces the likelihood of subsequent mis-alignment due to shipping or rough handling. The positioning system of '802 requires less space than prior art positioning systems, thereby allowing for a reduction in the overall size of the data storage system or allowing for an increased number of data cartridges to be stored within the system.
Regardless of the positioning system used, juke box data storage systems may be produced in a variety of sizes and configurations. In order to establish a product definition, a data storage system manufacturer may survey potential customers as to their specific needs. The manufacturer may then design a “point” product around this definition. This process may be repeated for different types of customers which are typically classified as “low-end”, “mid-range” or “high-end” customers (“low-end” customers requiring a more cost-competitive, smaller capacity library than “mid-range” or “high-end” customers). The result may be a series of products not only of different sizes and capacities, but also having unique housings, assemblies, and individual components.
Furthermore, the capacity of each of these products is limited, i.e., within any particular data storage system produced by a manufacturer there is a specific number of cartridge storage locations and drives. This limits the options for a customer whose needs change and who may require a larger data storage system at some point in the future. More particularly, that customer can either purchase another data storage system to use along with their original data storage system, or that customer can purchase a new, larger-capacity data storage system to replace the original one. While the former option involves less initial cost than the latter, there are several disadvantages for the customer to utilize multiple data storage systems rather than purchase a single, larger system. Specifically, each data storage system has its own cartridge access device, data storage racks and drives. There is an unnecessary duplication of components such as the cartridge access device: i.e., the customer needing an upgrade requires more data storage racks and possibly more drives, but not an extra cartridge access device. Furthermore, the magazines and drives from the first data storage system are not accessible by the cartridge access device of the second data storage system, and vice-versa.
Thus, a need exists for a data storage system which is comprised of individual modular units that can be combined to form data storage systems of varying size and capacity. Ideally, this modular data storage system would utilize the laterally expandable positioning system of '802 which is adapted to laterally translate a cartridge access device among all of the modular units.
The modular units would preferably be comprised of interchangeable housings, assemblies and individual components. This would allow the entire family of data storage systems, including systems for low-end, mid-range, and high-end customers, to be designed and manufactured together. This replication of components would provide many advantages to both the manufacturer and the customer, since a single set of components could be used to supply an entire family of data storage systems. To further avoid duplication of components, a power supply would most preferably be housed within a “master” modular unit which is electrically connectable to any “slave” modular units which require electrical power for drives or other electrically-powered components. The “master” modular unit could also be used to house various ancillary devices which need not be duplicated in the slave modular units, such as, for example, a control system which controls the positioning system.